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<blockquote data-quote="Umbran" data-source="post: 6737264" data-attributes="member: 177">I am going to be picky, because this is science, and we are talking about precision.The article says it has a speed of &quot;35 kilometers per second (78,000 mph)&quot;.&nbsp; These are, actually, both given with two significant digits.&nbsp; In the absence of other graphic elements telling us which are significant (a bar above or below the rightmost significant zero is common), you generally assume that all three trailing zeroes are not significant.&nbsp; The other indicator is that, typically, shifts in units of measure do not introduce or remove significant figures - so the km/sec and mph figures should have the same number of significant figures.&nbsp; <a href="https://en.wikipedia.org/wiki/Significant_figures" target="_blank">https://en.wikipedia.org/wiki/Significant_figures</a>Concise rules<ul>
<li data-xf-list-type="ul">All non-zero digits are significant</li>
<li data-xf-list-type="ul">Zeros between non-zero digits are significant.</li>
<li data-xf-list-type="ul">Leading zeros are never significant.</li>
<li data-xf-list-type="ul">In a number with a decimal point, trailing zeros, those to the right of the first non-zero digit, are significant.</li>
<li data-xf-list-type="ul">In a number without a decimal point, trailing zeros may or may not be significant. More information through additional graphical symbols or explicit information on errors is needed to clarify the significance of trailing zeros.</li>
</ul>By the way, if you are going to do a calculation in metric units, and they *hand* you a metric measurement (km/sec), it doesn't make a whole lot of sense to use the Imperial measure, and then convert it to metric.&nbsp; 35 km/s = 35,000 m/s, and off you go!</blockquote>

[QUOTE="Umbran, post: 6737264, member: 177"] I am going to be picky, because this is science, and we are talking about precision. The article says it has a speed of "35 kilometers per second (78,000 mph)". These are, actually, both given with two significant digits. In the absence of other graphic elements telling us which are significant (a bar above or below the rightmost significant zero is common), you generally assume that all three trailing zeroes are not significant. The other indicator is that, typically, shifts in units of measure do not introduce or remove significant figures - so the km/sec and mph figures should have the same number of significant figures. [url]https://en.wikipedia.org/wiki/Significant_figures[/url] [B]Concise rules[/B] [LIST] [*]All non-zero digits are significant [*]Zeros between non-zero digits are significant. [*]Leading zeros are never significant. [*]In a number with a decimal point, trailing zeros, those to the right of the first non-zero digit, are significant. [*]In a number without a decimal point, trailing zeros may or may not be significant. More information through additional graphical symbols or explicit information on errors is needed to clarify the significance of trailing zeros. [/LIST] By the way, if you are going to do a calculation in metric units, and they *hand* you a metric measurement (km/sec), it doesn't make a whole lot of sense to use the Imperial measure, and then convert it to metric. 35 km/s = 35,000 m/s, and off you go! [/QUOTE]

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